Fully rotating hook for a lock stitch sewing machine

ABSTRACT

A fully rotating hook .[.includes an outer member or rotary loop taker having a track groove therein and an inner shuttle member or bobbin case a projection extending into the groove. A spaced relation between the track groove and the projection is maintained by feeding compressed air into a clearance therebetween..]. .Iadd.assembly for a lock stitch sewing machine having an inner bobbin case for supporting a thread bobbin with a track projection extending circumferentially around the bobbin case, an outer loop taker mounted about the bobbin case and having a track groove extending circumferentially around an inner peripheral surface thereof and air passages for injecting compressed air into a clearance between adjacent surfaces of the projection and the groove. The air passages can be formed in the groove of the loop taker and in the projection. The projection includes a groove extending radially inwardly from a radially outermost surface and a plurality of exhaust holes extend from the groove to axial end surfaces of the projection. Compressed air is supplied to the air holes opening into the groove to thereby create an air film between the surfaces of the projection and the confronting surfaces of the groove..Iaddend.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention generally relates to a fully rotary or rotatinghook for a sewing machine and more particularly, to an improvedconstruction of a fully rotating hook for eliminating disadvantages dueto rotational friction between an inner shuttle member or bobbin caseand an outer shuttle member or loop taker.

2. Description of the Prior Art

In FIGS. 1 and 2 illustrating a prior art arrangement, there is shown avertical fully rotating hook 1 which is held at a needle descendingposition, with an inner shuttle member or bobbin case 3 accommodated inan outer shuttle member or rotary loop taker 2. In the inner bobbin case3, there is mounted a bobbin 11 for winding a bobbin thread therearound.The inner bobbin case 3 is stopped against rotation by an inner looptaker retaining member (not shown) which is fixed to a machine body.Along an outer peripheral surface of the inner bobbin case 3, there isformed an externally directed flange-like track projection 5 extendingin a circumferential direction partially throughout the circumference.This projection 5 is fitted into an internally directed flange-liketrack groove 6 extending in a circumferential direction along a portionof the inner peripheral surface of the outer loop taker 2. The outerloop taker 2 may be driven for rotation in one direction about an axisby a drive means (not shown) connected to a rotary shaft 16. Forrotating the outer loop taker 2 in the state where the inner bobbin case3 is stopped from rotation as described above, a lubricating oil or thelike is supplied between contact faces 4 of the track projection 5 ofthe inner bobbin case 3 and the track groove 6 of the outer loop taker 2so as to reduce friction between such two elements.

In this prior art device, however, during high speed rotation of thevertical fully rotating hook 1, friction still exists between the outerloop taker 2 and the inner bobbin case 3, even when the lubricating oilor the like is applied thereto, thus resulting in abrasion of the rotaryhook 1. Moreover, the thread or the like tends to be soiled by thelubricating oil, and thus it has been difficult to carry out a sewingoperation smoothly in an efficient manner.

SUMMARY OF THE INVENTION

Accordingly, it is a primary object of the present invention to providean improved fully rotating hook in which smooth movements between anouter shuttle member or rotary loop taker and an inner shuttle member orbobbin case can be achieved without employment of lubricating oil,thereby eliminating the technical problems described above.

In accomplishing the above object, the fully rotating hook for a lockstitch sewing machine according to the present invention includes anouter shuttle member or rotary loop taker having formed therein a trackgroove, with at least one air blast hole formed in the track groove. Aspaced relation is maintained between the track groove and a projectionof the inner bobbin case by jetting compressed air from the air blasthole into a clearance between the surfaces of the groove and theprojection.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of a conventional fully rotating hook,

FIG. 2 is a cross section taken along the line II--II in FIG. 1,

FIG. 3 is a longitudinal sectional view of a fully rotating hookaccording to one preferred embodiment of the present invention,

FIG. 4 is a view similar to a portion of FIG. 3, but of anotherembodiment of the invention,

FIG. 5 is a fragmentary cross sectional view on an enlarged scale of asection V in FIG. 4,

FIG. 6 is a top plan view of an inner shuttle member or bobbin caseaccording to a further embodiment of the present invention,

FIG. 7 is a fragmentary cross section taken along the line VII--VII inFIG. 6, and

FIG. 8 is a fragmentary cross section taken along the line VIII--VIII inFIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to FIG. 3, there is shown a longitudinal sectional view of onepreferred embodiment according to the present invention, in whichportions corresponding to like parts in the prior art arrangement ofFIG. 2 are designated by similar reference numerals, but followed by thesuffix "a".

In the arrangement of FIG. 3, an upper bobbin case member 8 is mountedwithin an inner shuttle member or lower bobbin case member 3a. A bobbin9 having wound therearound thread 7 is accommodated within members 3aand 8. A track projection 5a extends outwardly in the circumferentialdirection, partially throughout the circumference as in the prior artarrangement described above, from an outer peripheral surface of member3a, and projection 5a is fitted into a circumferentially extending trackgroove 6a formed in an inner peripheral surface 11 of outer shuttlemember or rotary loop taker 2a throughout a portion of thecircumference. In the track groove 6a of the outer loop taker 2a, one ormore air blast holes 12 are formed to confront an outer portion 13 ofthe projection 5a of member 3a. These air blast holes 12 arecommunicated with a hollow portion or passages 14 of the outer looptaker 2a.

Into a bottom portion 15 of the outer loop taker 2a is fitted one end ofa cylindrical rotary shaft 16a which is positioned coaxially with theaxis of outer loop taker 2a. The hollow portion 14 of the outer looptaker 2a is communicated with a hollow portion or passage 19 of therotary shaft 16a, while a fitting 20 between the outer loop taker 2a andthe rotary shaft 16a is fixed by fixing members 17 and 18 so as toachieve airtightness.

In the vicinity of a central portion of the rotary shaft 16a, there areprovided vent holes 22 and 23. A cylindrical pipe joint 21 is coaxiallymounted about the rotary shaft 16a in a manner to cover vent holes 22and 23. The pipe joint 21 has an inner diameter slightly larger than anouter diameter of the rotary shaft 16a, and a clearance 24 between thepipe joint 21 and the rotary shaft 16a is communicated with the hollowportion 19 of the rotary shaft 16a through the vent holes 22 and 23. Atpositions bridging the vent holes 22 and 23 of the rotary shaft 16a inthe clearance 24, there are mounted O rings 25, 26, 27 and 28 whichcontact the outer peripheral surface of the rotary shaft 16a incircumferential directions. These O rings 25 to 28 are respectivelyfitted into concave grooves 29, 30, 31 and 32 extending incircumferential directions along the inner peripheral surface of thepipe joint 21. Concave grooves 29 and 32 prevent displacement of thepositions of the O rings 25 to 28. Owing to the O rings 25 to 28 mountedto bridge the vent holes 22 and 22 in the manner described above, it ispossible to prevent air leakage through the clearance 24 between thepipe joint 21 and the rotary shaft 16a. Moreover, at opposite axial ends33 and 34 of the pipe joint 21, there are provided bearings 35 and 36which rotatably support the rotary shaft 16a extending through the pipejoint 21.

The clearance 24 between rotary shaft 16a and the pipe 21 leading to thehollow portion 19 of the rotary shaft 16a is communicated with a hollowportion or passage 38 of an air feed pipe 37 extending from the pipejoint 21, with the end portion of the air feed pipe 37 being connectedto an air compressor pump, not shown.

The compressed air fed from the air compressor pump passes through theair feed pipe 37 and is fed from clearance 24 through vent holes 22 and23 into the hollow portion 19 of the rotary shaft 16a. The compressedair is further fed from the hollow portion 19 of the rotary shaft 16athrough the hollow portion 14 of the outer loop taker 2a and through theair blast holes 12. Thus, the compressed air is jetted from the airblast holes 12 into a clearance 4a between the track groove 6a and theprojection 5a. As a result, an air film is formed in the clearance 4a,and thus, the sliding resistance or friction between the rotating trackgroove 6a and the stationary projection 5a are eliminated.

By providing the air blast mechanism as described above in the outerloop taker 2a, high speed operations at speeds of more than 5000 to 6000stitches per minute, which are considered to be a limit in sewingmachines employing conventional fully rotating hooks, may beadvantageously realized. Moreover, through elimination of the slidingresistance between the outer loop taker 2a and the inner bobbin case 3a,sliding noises occurring in conventional hooks are eliminated, with aconsequent elimination of an unpleasant atmosphere for operators of thesewing machine. Furthermore, since air under high pressure is directedtowards the inner bobbin case 3a at all times, it is possible tosimultaneously obtain a cleaning effect and cooling effect for the fullyrotating hood 1a. It is to be noted that materials for the inner bobbincase 3a may be light weight alloys, plastics, etc.

FIG. 4 is a longitudinal sectional view of another embodiment accordingto the present invention, while FIG. 5 is a cross sectional view showinga section V in FIG. 4 on an enlarged scale. The construction of FIG. 4resembles that of FIG. 3, with corresponding parts being designated bysimilar reference numerals, but followed by the suffix "b". A trackprojection 5b of the inner shuttle member or bobbin case 3b is fittedinto the track groove 6b of the outer shuttle member or loop taker 2a.In the track groove 6b are formed air blast holes 43, 45 and 44respectively confronting side portions 40 and 41 and outer portion 42 ofthe projection 5b. Blast holes 43 to 45 are communicated with a hollowportion 14b of the outer loop taker 2a. By jetting the compressed air inthe three illustrated directions shown in FIG. 5, the surfaces of theprojection 5b and the track groove 6b may be positively maintained inspaced relation from each other, and the functions of the fully rotatinghook 1b further will be improved.

FIG. 6 is a top plan view of an inner shuttle member or bobbin case 3caccording to a further embodiment of the present invention. FIG. 7 is across section taken along the line VII--VII in FIG. 6, and FIG. 8 isalso a cross section taken along the line VIII--VIII in FIG. 6. In anouter portion 51 of a track projection 5c of the inner bobbin case 3c isformed a circumferential concave groove 52. At least one or moreelongated openings 12c are provided in a track groove 6c to confrontgroove 52. Also, exhaust holes 50 connected with concave groove 52 areformed in projection 5c to extend in vertical upward and downwarddirections. The exhaust holes 50 are provided at spaced intervals in thecircumferential direction of the projection 5c .Iadd.and the exhaustholes 50 extend axially from the circumferential groove 52 to axial endsurfaces of the projection 5c.Iaddend..

The compressed air fed from the compressor pump is jetted from theelongated openings 12c of the outer loop taker into the concave groove52 of the projection 5c of the inner bobbin case 3c, and is dischargedthrough the exhaust holes 50 connected with the concave groove 52. Bydischarging the compressed air from the exhaust holes 50 extending inthe upward and downward directions of the projection 5c as describedabove, a spaced relation between the surfaces of projection 5c and thetrack groove 6c may be positively achieved.

The vertical fully rotating hook according to each embodiment of thepresent invention may be readily coupled with the air jetting device 60shown in FIG. 3, without requiring a large-scale remodeling of theconventional sewing machine. Moreover, the present invention may also beapplied to a horizontal fully rotating hook as well.

As is clear from the foregoing description, according to the presentinvention it is possible to prevent the rotating hooks from beingabraded due to high speed rotation by eliminating the undesirablesliding resistance or friction between the inner shuttle member orbobbin case and the outer shuttle member or loop taker throughemployment of compressed air. Furthermore, owing to the elimination ofsoiling of threads and the like by oil as experienced in conventionalarrangements, the fully rotating hook according to the present inventionprovides marked improvements of the sewing performance and productivity.

The invention may be embodied in other specific forms without departingfrom the spirit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

I claim:
 1. In a .[.vertically oriented.]. fully rotating hook assemblyfor a lock stitch sewing machine and being of the type including aninner bobbin case for supporting a thread bobbin, said bobbin casehaving formed on an outer peripheral surface thereof a track projectionextending circumferentially of said bobbin case over a portion of thecircumference thereof, an outer loop taker mounted about said bobbincase.[.,.]. said loop taker having formed in an inner peripheral surfacethereof a track groove extending circumferentially of said loop takerover a portion of the circumference thereof, means for rotating saidloop taker about .[.a vertical.]. .Iadd.an .Iaddend.axis such thatrelative rotation occurs between said loop taker and said bobbin case,with such rotation being guided by said projection fitting within saidgroove, and means for reducing friction during such rotation betweenadjacent surfaces of said projection and groove, the improvement whereinsaid friction reducing means comprises:means for injecting compressedair into a clearance between said adjacent surfaces and thereby forforming .Iadd.an .Iaddend.air .[.films.]. .Iadd.film .Iaddend.between.[.upper, lower and radially outermost.]. said .Iadd.adjacent.Iaddend.surfaces of said projection and .[.adjacent complementary saidsurfaces of.]. said groove; said injecting means comprising at least oneair passage formed in said loop taker, a plurality of air holes openinginto said groove and connected to said air passage, and means forsupplying compressed air to said air passage and thereby injecting thecompressed air through said air holes into said clearance; saidsupplying means comprising said rotating means being in the form of ahollow rotatable shaft fixed to .[.the bottom of.]. said loop taker,said shaft having therethrough a passage connected to said air passagein said loop taker, said shaft having therethrough a hole connected tosaid passage in said shaft, and means for introducing compressed airthrough said hole into said passage in said shaft; and said introducingmeans comprising a pipe fixed in position surrounding a portion of saidshaft having therein said hole, said shaft being rotatable within saidpipe, means defining a sealed clearance between said shaft and saidpipe, said sealed clearance being connected to said hole, and an airfeed pipe connected to said pipe for supplying compressed airtherethrough and into said sealed clearance.
 2. In a .[.verticallyoriented.]. fully rotating hook assembly for a lock stitch sewingmachine and being of the type including an inner bobbin case forsupporting a thread bobbin, said bobbin case having formed on an outerperipheral surface thereof a track projection extendingcircumferentially of said bobbin case over a portion of thecircumference thereof, an outer loop taker mounted about said bobbincase, said loop taker having formed in an inner peripheral surfacethereof a track groove extending circumferentially of said loop takerover a portion of the circumference thereof, means for rotating saidloop taker about .[.a vertical.]. .Iadd.an .Iaddend.axis such thatrelative rotation occurs between said loop taker and said bobbin case,wtih such rotation being guided by said projection fitting within saidtrack groove, and means for reducing friction during such rotationbetween adjacent surfaces of said projection and track groove, theimprovement wherein said friction reducing means comprises:means forinjecting compressed air into a clearance between said adjacent surfacesand thereby for forming .Iadd.an .Iaddend.air .[.films.]. .Iadd.film.Iaddend.between .[.upper, lower and radially outermost.]. said surfacesof said projection and .[.adjacent complementary said surfaces of.].said track groove, said injecting means comprising a groove formed insaid projection and extending radially inwardly from .[.said.]. .Iadd.a.Iaddend.radially outermost surface thereof, a plurality of exhaustholes extending .[.vertically.]. .Iadd.axially .Iaddend.from saidinwardly extending groove to .[.said upper and lower.]. .Iadd.axial end.Iaddend.surfaces of said projection, at least one air passage formed insaid loop taker, a plurality of air holes in said loop taker, said airholes being connected to said air passage and opening into said trackgroove at a position confronting said inwardly extending groove in saidprojection, and means for supplying compressed air to said air passageand thereby injecting the compressed air through said air holes and saidclearance and radially inwardly into said inwardly extending groove,whereby said exhaust holes then discharge said compressed air.[.vertically upwardly and downwardly.]. .Iadd.axially .Iaddend.fromsaid .[.upper and lower.]. .Iadd.axial end .Iaddend.surfaces.